A printed circuit board and system level interconnect test is a high priority need in industry. This is particularly so in the automotive industry where many different phases of electronic activity, from IC design to vehicle warranty and customer service, are present and thus involve several areas of testing and diagnostics. At the IC level a significant amount of testing of mixed-signal devices is required. In order to meet the electronic test and diagnostic needs of the automotive industry, the Design-for-Testability (DFT) real estate (both pin count and silicon) must be kept to a minimum in order for the cost to justify the benefits.
The extended period of vehicle warranty requires significant field test and diagnostic capability, and hierarchial testing concepts are required, beginning at the integrated circuit (IC) level and extending to the discrete components on mixed-signal boards and peripheral analog elements in control systems. The increasing trend to integrate greater capability into IC's, resulting in embedded complexities, has significantly reduced the effectiveness of the present in-circuit testing methods at the board level via a "bed of nails" interface. There is therefore a need to provide a "virtual in-circuit" testing at all levels over an analog test bus.
IC, subsystem and system level DFT approaches should entail structures that provide a means for testing for analog drift trends at critical locations within the IC's, PC boards and systems. Data paths to failure under harsh operating conditions are required to establish appropriate warranty data. Pertinent data feedback over the life of the product to all levels of the process would enhance continuous improvement and project future requirements amidst increasing complexities.